A nationally renowned San Francisco surgeon is presumed dead after vanishing while abalone diving off the Mendocino County Coast this weekend.

A search and rescue team found an abalone pry bar and measuring tool belonging to William Krupski on Monday near the spot where he was last seen at Big Rock, about 200 yards off Van Damme State Park, south of the coastal town of Mendocino.

No other sign of Krupski was found, Mendocino County Sheriff's Lt. Don Miller said.

Krupski, a vascular surgeon at Kaiser-Permanente Medical Center in San Francisco, was abalone diving Saturday with his wife, Ann, on what has become an annual birthday dive; he would have turned 57 on Monday. Krupski took up the sport some 20 years ago, and got his wife involved about five years ago, his family said.

The floats the couple were using drifted away in a strong current; Krupski's wife swam about 30 yards to retrieve them while he continued diving, according to Miller and family members. She told sheriff's investigators that her husband was gone when she returned.

"We know by what his wife told us that he was tired, but he was also intent on getting the last of the three abalone you are allowed to get on a sport fishing license," said Miller, who is an abalone diver himself. "We don't know what happened. No one witnessed it."

The waters where the couple were diving, near the mouth of the Little River, are favored by abalone divers because it is usually calmer than the open sea. Winds that day were particularly strong, gusting at 35 mph, and there were rough seas, Miller said, adding the Krupskis were not the only abalone divers out there.

A shark attack is unlikely, Miller said, because none was spotted by anyone that day, and there was no blood in the water. He said any number of things could have caused Krupski to drown, from knocking into a rock to getting caught in kelp.

"The only thing I can bet did not happen is that he did not release his weight belt," Miller said. "The first thing a diver is supposed to do when they get in trouble is kick that weight belt off, but most people when they are in panic mode don't think of the weight belt."

Coast guard helicopters and boats searched Saturday afternoon and Sunday. Krupski's "ab iron" and measure were found Monday by the Mendocino County Sheriff's Department Swift Water and Dive Team. Miller promised to continue searching until a body is found or something definitive is known about Krupski's fate.

Krupski became the assistant sub-chief of vascular surgery at Kaiser in 2003 after more than a decade at the University of Colorado Health Science Center, where he was chief of vascular surgery. Before that, he had been with the San Francisco Veterans Administration Hospital.

Bruce Blumberg, the physician-in-chief at Kaiser San Francisco, said Krupski is nationally recognized for his work in abdominal aortic aneurysms, carotid artery surgery and coronary artery and peripheral arterial disease. He has lectured extensively at medical symposiums and was often called as an expert witness in court, according to his family.

"It's rough. It's a shock, but he was doing something that made him happy, " said his son, Matt Krupski. "There's always hope, but realistically it's been since Saturday night. I'm just hoping he's found."